We report high-resolution angle resolved photoemission measurements on single crystals of Pt${}_2$HgSe${}_3$ grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001)-projection separates the surface Brillouin zone in topological and trivial areas. In the non-trivial $k$-space range we find surface states with multiple saddle-points in the dispersion resulting in two van Hove singularities in the surface density of states. Based on density functional theory calculations, we identify these surface states as signatures of a topological crystalline state which coexists with a weak topological phase.

中文翻译：

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双拓扑半金属Pt2HgSe3的体和表面电子结构

我们报告了P​​t单晶的高分辨率角度分辨光发射测量${}_2$汞硒${}_3$通过高压合成生长。我们的数据显示出一条带缝隙的狄拉克结线，其（001）投影将拓扑和琐碎区域中的表面布里渊区分开。在平凡中$ķ$在空间范围内，我们发现在色散中具有多个鞍点的表面状态会导致状态的表面密度出现两个van Hove奇点。基于密度泛函理论计算，我们将这些表面状态标识为与弱拓扑相共存的拓扑晶体状态的特征。